Known circuit breakers have two contact pieces, each having a consumable contact (tulip and pin), which can be disconnected as desired. Either only one contact piece or both contact pieces can be moved for disconnection. In another case, a drive can drive the tulip, and a transmission or auxiliary transmission transmits the movement of the tulip to the pin. For example, linear transmissions having a transmission ratio of 1:1 can be used, as disclosed in EP 0 822 565 or U.S. Pat. No. 5,478,980. The transmission ratio of the transmission is defined as the ratio of a movement speed or movement distance of the movement transmitted or produced by the transmission (output drive movement, such as a movement of the pin) to a movement speed or movement distance of a movement which drives the transmission (drive movement, such as a movement of the tulip).
Constant transmission ratios can also be provided which are greater than 1:1. In this case, at a given drive speed, the relative speed between the two contact pieces is increased, as a result of which the switch contacts can be disconnected more quickly. However, as the constant transmission ratio increases, the travel of the contact piece on the output drive side increases, and therefore the physical length of the quenching chamber increases, as well.
Transmissions with a transmission ratio which is not constant are likewise known. Transmissions such as these are disclosed, for example, in EP 0 992 050, EP 1 211 706 and DE 100 03 359.
EP 0 809 269 discloses an auxiliary transmission having a double-ended lever arm which is mounted in a fixed position such that it can rotate. At one end, the lever arm has an elongated hole for engagement for a driving tie rod which can be moved axially, and at the other end it has a fixed-articulated lever for transmitting force to the opposing contact.
EP 0 696 040 discloses an auxiliary transmission with a gearwheel which is mounted in a fixed position such that it can rotate. The gearwheel is driven by a toothed rod. A lever is articulated at a fixed predetermined position on the gearwheel surface in order to transmit force to the opposing contact.
However, transmissions with a transmission ratio that is not constant can occupy a large amount of physical space. The time profile of the transmission ratio of these transmissions is also often unsatisfactory.
The complete disclosures of all of the documents mentioned herein are incorporated by reference in their entireties.